1. Field of the Invention
The present invention relates to a glass for substrate to be used for e.g. a substrate for a data storage medium such as a magnetic disc or an optical disc, or a substrate for a flat display such as PDP (plasma display panel) or a FED (field emission display), and a glass substrate.
2. Discussion of Background
Soda lime silica glass is widely employed as a glass for substrate to be used for e.g. a substrate for a data storage medium or a substrate for a flat display panel.
However, a substrate made of soda lime silica glass has had a problem that the surface conditions are likely to substantially change during the stock due to so-called a corrosion phenomenon. Especially, in the case of a magnetic disc substrate, a layer such as an undercoat layer, a magnetic layer or a protective layer formed on the substrate is likely to be peeled.
By chemical strengthening treatment, soda lime silica glass may be made to be scarcely susceptible to a corrosion phenomenon. However, such chemical strengthening treatment brings about a problem that the number of process steps is obliged to increase, and a stain tends to deposit on the surface of the substrate after the chemical strengthening treatment.